This invention relates to the art of self-closing gates or barriers that permit passage in one direction, but not in the other direction.
For example U.S. Pat. No. 5,615,520 granted to John D. McGuire provides for a one-way gate for allowing passage in one direction whose internal mechanical works are concealed within an enclosure, those mechanical works including independent means to perform three function of, first, biasing the gate to return to a closed position; second, limiting the range of motion of the gate between a closed position and a fully open stop; and third, providing a damper to retard the motion of the gate.
Some prior art self-closing gates or barriers permit a person to gain passage through said one-way gate in a direction opposite to said one direction by displacing said gate or barrier said one direction and passing through the resulting unobstructed passageway. There is a need therefore for entrance devices which prevent the one-way gate or barrier from being "tampered" in this way. For example, WO 93/23799 provides for at least one entrance gate, and a system for controlling entrance through said entrance gates comprising, first, entrance passageway defined by posts on which gates are pivotally mounted; second, a sonar sensor means which functions to detect the presence of people and objects in the vicinity of the passageway and to deliver signals to a control means for controlling opening and closing of the gate; wherein said sonar sensor means includes at least one sonar which is mounted in or in the vicinity of the passageway.
The prior art entrance device utilizing sonar is complicated in that said entrance device requires, first, a sonar emitting device; second, an electronic unit for amplifying sonar pulses; third, a microprocessor for sampling said sonar signals; fourth, a microprogram operably associated with said microprocessor for processing said sonar signals to a further microprocessor which controls opening and closing of the gates. Operation of said prior art entrance device utilizing sonar also requires configuration of said microprocessors to store input related to a defined external measuring area within which objects are detected by said sonar sensing means.
There is a need therefore for an entrance device of simple construction that is easy and inexpensive to produce, that can be installed without difficulty, and which is easy to operate.